The present invention is directed to a vacuum-packaging machine in which are produced sealed vacuum-packages of food, such as cold cuts, hot dogs, cheese, and the like. The conventional vacuum-package machine transports a bottom film-layer, which bottom film-layer has been formed into a series of pockets in which has been placed the food-product, to a sealing station, at which sealing station an upper film-layer is placed over, and sealed to, the bottom film-layer, whereby there are formed packages. The packages are evacuated at the sealing station, in order to form a vacuum-package. In the conventional vacuum-package machine, at the sealing station, there are provided an upper tool and a lower tool. The upper tool holds the upper film-layer by suction, while the lower tool holds down the bottom, film-layer, during evacuation and during the sealing process. Also provided at the sealing station, between the upper and lower tools is a nozzle-bar, or head, which is used for evacuating the packages. The nozzle-head extends the full width of the machine, and is coupled to a vacuum-source. The nozzle-head is activated until the packages at the sealing station have been evacuated, and then the packages are sealed completely about their edges.
The conventional vacuum-packaging machine is also often used to inject a protective gas into the packages, for extending shelf-life, which process is called gas-flashing. The gas used may be nitrogen or CO.sub.2, or mixtures thereof. Gas-flashing also helps to ensure that individual slices of the meat or cheese in the package to do not stick together, and to make the package appear more full of product. In the conventional vacuum-packaging machine, the gas-flashing is accomplished with the same nozzle-head used for evacuating the packages. In the conventional vacuum-packaging machine, just before the package is sealed adjacent the nozzle-head, the a protective gas is injected into the packages, after which the sealing of the packages occurs.
A problem associated with gas-flashing as it is conventionally done, is that, when the nozzle-head is used to evacuate the packages, it draws out of the packages some particles of food. These particles of food, therefore, accumulate in the nozzle-head, or in the connecting hose therefor. These food particles, no matter how minute, form bacteria in the nozzle-head and connecting hose. Thus, when the very same nozzle-head is used to inject the protective gas into the packages via the very same path, these particles of food with bacteria are forced back into the packages. The bacteria adversely affect the shelf-life of the product in the packages, by causing the product to spoil prematurely, which at least partially defeats the very intent of the gas-flashing process.
The present invention overcomes this problem of re-injecting the bacteria-tainted food particles into the packages.